Protection Device

a protection device and polymer technology, applied in the direction of resistor details, protective switch details, relay details, etc., can solve the problems of large device itself, inconvenient use of ptc devices in mobile electronic devices, and inability to sense relatively low abnormal elevated temperatures. , to achieve the effect of simple construction and large capacity

Inactive Publication Date: 2010-01-21
TYCO ELECTRONICS RAYCHEM KK
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Benefits of technology

[0025]With the protection device of the present invention, as a result of the shape memory alloy lead assuming the function of sensing an abnormal elevated temperature, the degree of freedom in selecting the polymer PTC device having the function of sensing abnormal current is increased. As a result, a polymer PTC device having a large capacity may be used so that a protection device that is small in size and wherein the abnormal elevated temperature that is sensed is low. Further, the construction of this protection device is very simple as it only has the shape memory alloy lead and the polymer PTC device connected by an electrically conductive adhesive.

Problems solved by technology

Therefore, the commercially available polymer PTC devices cannot accommodate the need to sense relatively low abnormal elevated temperatures.
However, if such a lower melting point polymer is used, the size of the device itself is increased when trying to make a large current capacity polymer PTC device, and such a polymer PTC device is not suitable for use in a mobile electronic apparatus.
In sensing overheating and / or excessive current, this protection device performs a similar function as the above described polymer PTC device, but the construction of the protection device is very complicated, as two types of springs are placed within the metal case and the PTC device needs to be retained in the movable state.
Further, the PTC device and the other lead is in the abutting state but not connected permanently as with soldering, so that arcing may occur between the PTC device and the other lead when there is excessive current flow.
There is a problem in that, when arcing occurs and the PTC device and the other lead are contact welded, the device will not function as a protection device.[Patent Reference 1] Japanese Patent Laid-Open Publication No. 2002-15902

Method used

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Example 1

Manufacturing of Protection Device

[0042]Using the elements below, the protection device of the present invention was connected to a wiring substrate, as shown in FIG. 2(a) (however, only the shape of the shape memory alloy lead is different, as described below):

(1) Polymer PTC Device (manufactured by Tyco Electronics Raychem K.K.)[0043]Product name: PolySwitch (holding current capacity: 2.0 A (at 70° C.), trip temperature: 125° C.)[0044]Size: 3.4 mm×3.6 mm (thickness 0.5 mm)[0045]Polymer PTC element (polyethylene+nickel filler)[0046]Metal electrode: gold-plated nickel (thickness: 0.03 μm)

(2) Shape memory alloy lead (manufactured by K.K. Furukawa Techno Material, Ni—Ti—Cu)[0047]Product name: NT Alloy[0048]Size: OD 0.75 mm×approx. 10 mm[0049]Shape: Linear wire shape before recovery->bent wire shape after recovery[0050]Recovery temperature: 80° C.

(3) Conductive adhesive (manufactured by Fujikura Chemical)[0051]Product name: Dotite D-500[0052]Thermoplastic resin: acrylic resin...

example 2

Confirmation of Action of Protection Device

[0056]When current at 20 A / 6V was applied at 25° C. to the substrate provided with the protection device as described above, the polymer PTC device 18 tripped, after which the shape memory alloy lead was actuated by the heat generated by the polymer PTC device, and the current flowing through the circuit was substantially cut off.

[0057]When current at 100 mA / 6V (the PTC device never trips under this conditions) was passed through another substrate provided with the protection device as described above and the temperature around the substrate raised gradually from 50° C.; so that the ambient temperature reached 80° C., the circuit in which the protection device was inserted was opened as the linear shape memory alloy lead recovered and became bent, thus separating from the electrically conductive adhesive 22 (see FIG. 2(b); it is noted that the shape of the lead 20 is bent).

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Abstract

It is provided a new protection device with a large current capacity, which can sense a relatively low abnormal temperature, and further has a simple construction and is not large in size. The protection device comprises (1) a polymer PTC device (18) having metal electrodes (14, 16) on the both main surfaces, and (2) a shape memory alloy lead (20), wherein the shape memory alloy lead is connected to the polymer PTC device by an electrically conductive adhesive (22) containing a thermoplastic resin and an electrically conductive filler.

Description

FIELD OF THE INVENTION[0001]The present invention relates to a protection device having a PTC device, specifically a protection device having a PTC device with a shape memory alloy lead connected thereto, and a method of manufacturing such a protection device.BACKGROUND ART[0002]A polymer PTC device is used as a protection device to prevent the discharge / charge of excessive current and overheating of a battery pack in a mobile electronic apparatus such as a cellular phone. The polymer PTC device comprises a polymer PTC element, composed of an electrically conductive polymer composition containing a polymer and conductive filler dispersed therein, and metal electrodes disposed on both sides of the polymer PTC element, and the device is placed in close contact with the battery pack. The PTC device performs two functions, one of sensing an abnormally elevated temperature caused by a defect in the battery pack or an overheated condition around the battery pack (hereinafter also called “...

Claims

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Application Information

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Patent Type & Authority Applications(United States)
IPC IPC(8): H01H71/00
CPCC22C14/00H01C1/1406H01C7/027H01H2037/768H01H37/323H01H37/761H01C7/126H01C7/22H01H37/32
Inventor KOYAMA, HIROYUKI
Owner TYCO ELECTRONICS RAYCHEM KK
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